Island Lake is a class 27 lake located in the far northwestern part of Itasca County, two miles south of Northome, MN. The lake has one main public access on the northwest side and moderate shoreline development. The 2007 lake management plan indicates walleye and northern pike as the primary species of management with yellow perch as a secondary species. In 2003, a 24 to 36 inch protected slot length limit with only one northern pike over 36 inches in possession was implemented. Two years later a walleye slot length limit was applied to the lake that required all fish between 17 and 26 inches to be released and only one fish over 26 inches could be in possession.
Walleye catch rates have fluctuated from a low of 0.9/gill net in 1984 to a high of 10.1/gill net in 2006. In 2010, the walleye gill-net catch rate of 5.8 fish/net was near the management goal of 6 fish/net. The catch exceeded the lake class median of 5.5 fish/gill net. The sampled fish ranged from 8.5 to 24.0 inches and averaged 16.9 inches. The size structure goals were achieved in this assessment.
Walleye age and growth information was determined from scale, opercle, and otolith analysis. Thirteen year-classes were identified with fish from one to 14 years old present. All of the strong year classes (2002, 2005, and 2006) would have experienced multiple years of angler harvest by the time of this assessment. Walleye averaged 15.2 inches after four years of growth. Growth was similar to statewide averages through age 8. Slower growth after age 8 appears to be influenced by low sample size and older males.
Northern pike gill-net catch rates have ranged from a low of 1.1 fish/net in 1954 to a high of 11.7 fish/net in 1969. The northern pike gill-net catch was 9.2 fish/net in 2006 and declined to 6.3 fish/net in 2010, remaining near the management goal of 6.0 fish/net. The sampled fish ranged from 17.2 to 31.0 inches and had a mean length of 24.2 inches. The size structure goal of having PSD and RSD-P of 40 and 15 were almost achieved; PSD and RSD-P values were 81 and 10. Even the smallest northern pike sampled were sexually mature for both males and females. Seven year-classes were identified from cliethra and scales ranging from age 1 to age 7. Recruitment appears to be consistent. Fish estimated to be from the 2005 year class were the most common. Northern pike averaged 23.3 inches after four years of growth, which was above the statewide average of 20.5.
Yellow perch gill-net catch rates have fluctuated from a low of 15.2 fish/net in 1954 to a high of 151.8 fish/net in 1969. In the last three assessments, the gill net catch was 39.1 fish/net in 2003, 93.7 fish/net in 2006, and 39.7 fish/net in 2010. The catches have approached or exceeded the lake class 3rd quartile of 46.3 fish/gill net. The sampled yellow perch ranged from 5.2 to 12.0 and had a mean length of 7.4 inches. Age and growth information was not collected in this assessment.
Tullibee can be difficult to catch because they frequently live over deep water, an area our standard sampling gear was not designed to sample. As a result, catch rates can be highly variable. However, they are important to fish communities as a prey source for many predator species, especially northern pike and walleye. The catch rates from the last four assessments are an example of the highly variable nature of tullibee catches: the catch was 8.6 fish/net in 1997 (2nd highest for the lake), six years later, the catch was 1.7 fish/net, the catch was 11.8 fish/net in 2006 (highest on record for lake), and in 2010, the catch was 0.4 fish/net (lowest on record). The fish sampled in 2010 ranged from 8.3 to 12.7 inches and averaged 10.5 inches. Two distinct size groups in the length distribution would indicate two year classes were present.
Bluegill had never been sampled with trap nets prior to 1997, when 11.5 fish/net were sampled. Since 1997, the trap net catch rates have declined to 0.7 fish/net in 2003, increased to 4.7 fish/net in 2006, and declined to 0.3 fish/net in 2010. The sampled bluegill ranged from 3.2 to 9.3 inches. Age and growth information was not collected in this assessment.
Other species observed during the population assessment included black crappie, pumpkinseed sunfish, rock bass, smallmouth bass, and white sucker.